Desalination unit with electricity generation

ABSTRACT

A system for processing saltwater or brackish water while recovering energy otherwise wasted in electricity generation by a natural gas generator or turbine. Heat in the generator exhaust is used to directly heat and process the water in the saltwater or brackish water into high quality steam, separating the majority of salt and contaminants from the water, and leaving potable water that can be permitted and released to the environment or sold for agricultural or industrial use such as oilfield activities. The system also captures and liquefies CO2 in the generator exhaust.

This application claims benefit of and priority to U.S. ProvisionalApplication No. 62/354,923, filed Jun. 27, 2016, and is entitled to thatfiling date for priority. The specification, figures, and completedisclosure of U.S. Provisional Application No. 62/354,923 areincorporated herein in their entireties by specific reference for allpurposes.

FIELD OF INVENTION

This invention relates to a desalination unit for saltwater treatmentand disposal. More particularly, this invention relates to adesalination unit with a natural gas electrical generator that treatssaltwater from a variety of sources, such as produced water fromoilfield operation, or saltwater or brackish water at a desalinationplant for creation of potable water.

BACKGROUND OF INVENTION

Various processes for the desalination of saltwater and brackish waterare known in the art. Examples of processes and system for desalinationare disclosed in el Din Nasser, U.S. Pat. No. 4,511,436; Weinberger, etal., U.S. Pat. No. 5,582,690; and Kamiya, et al., U.S. Pat. No.6,391,162; all of which are incorporated herein in their entireties byspecific reference for all purposes. In general, desalination processesapply some form of energy, such as heat, to the saltwater and brackishwater, causing the water to evaporate or vaporize, leaving behind saltand other contaminants.

Gas-powered turbines and electrical generators also are known in theprior art. Examples of gas-powered turbines and generators are disclosedin Yamanaka, et al., U.S. Pat. No. 7,114,322 and Ziegenfuss, U.S. Pat.No. 7,958,716, both of which are incorporated herein in their entiretiesby specific reference for all purposes. Electrical generators of thissort produce exhaust streams with excess heat and various gases, such ascarbon dioxide. Such exhaust streams often are wastefully emitted intothe ambient environment.

SUMMARY OF INVENTION

In various embodiments, the present invention comprises a saltwater orbrackish water processing system that receives and stores saltwater inone or more storage areas or tanks. The saltwater can come from avariety of sources, such as produced water from oilfield operation, orsaltwater or brackish water at a desalination plant for creation ofpotable water. From the storage area or tanks, the saltwater is directedto a or desalination plant or facility or heat exchanger connected to anatural gas electrical generator, which may be operated for a variety ofpurposes, such as, but not limited to, generating electricity through atransformer to be sold to a local electric utility grid, or to be usedlocally for private electric power purposes.

Heat created by the natural gas generator during generation ofelectricity exits through an exhaust flue, and is used to heat andprocess the saltwater in the heat exchanger. The application of heatturns the water in the saltwater into high quality steam, therebyseparating the majority of salt and contaminants in the saltwater fromthe water. The steam is condensed as potable water and directed into acooling pond or apparatus, and subject to further treatment, ifnecessary. The potable water can then be discharged into a localwaterway (with proper permitting), or used for local irrigation oragricultural purposes. In a further embodiment, high quality carbondioxide (CO₂) from the generator flue exhaust also is recovered,converted to liquid, and sold for industrial processes or used locally,such as, but not limited to, in a greenhouse.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a view of a system in accordance with an embodiment of thepresent invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In various exemplary embodiments, as seen in FIG. 1, the present systemprovides a saltwater processing system that receives and storessaltwater in one or more storage areas or tanks 10. The saltwater cancome from a variety of sources, such as produced water from oilfieldoperation, or saltwater or brackish water at a desalination plant forcreation of potable water.

From the storage area or tanks, the saltwater is directed to a ordesalination plant or facility or heat exchanger 30 connected to anatural gas electrical generator 20, which may be operated for a varietyof purposes, such as, but not limited to, generating electricity througha transformer 22 to be sold to a local electric utility grid 24, or tobe used locally for private electric power purposes. Heat created by thenatural gas generator during generation of electricity exits through anexhaust flue, and is used to heat and process the saltwater in the heatexchanger 30. The application of heat turns the water into high qualitysteam, thereby separating the majority of salt and contaminants in thesaltwater from the water.

The steam is condensed in a condenser or similar unit as potable waterand directed into a cooling pond or apparatus 40, and subject to furthertreatment, if necessary. The potable water 42 can then be dischargedinto a local waterway (with proper permitting), or used for localirrigation or agricultural purposes.

In a further embodiment, high quality carbon dioxide (CO₂) 50 from thegenerator flue exhaust also is recovered (such as through a carbondioxide scrubber), converted to liquid, and sold for industrialprocesses or used locally, such as, but not limited to, in a greenhouse.Examples of processes for removing and liquefying carbon dioxide fromsuch exhaust streams are described in Fujii, et al., U.S. Pat. No.5,344,627; Rongved, U.S. Pat. Nos. 6,180,012; and 8,828,130; all ofwhich are incorporated herein in their entireties by specific referencefor all purposes.

There are multiple revenue streams generated by the present system.First is the revenue derived for handling oilfield saltwater processingand disposal. The present invention further possesses the advantage ofavoiding injection of the saltwater into the underground strata, andthereby avoids adverse environmental impacts such as, but not limitedto, downhole pumping, chemical dumping, groundwater contamination, andearthquakes or earth movements.

The second revenue stream is the revenue received from sale of theelectricity generated. The third revenue stream is the revenue receivedfrom sale of the potable water. And a fourth revenue stream is therevenue received from sale of the processed carbon dioxide.

The system thus processes saltwater while recovering energy otherwisewasted in electricity generation by the natural gas generator. Thepresent invention uses the heat and carbon dioxide in the generatorexhaust to achieve a very high efficiency gain efficiency gain, therebyproviding a cost-effective, environmentally-sound solution for oilfieldand brackish saltwater treatment and disposal. In one exemplaryembodiment, the present invention results in an overall 80% efficiencygain.

The natural gas generator has multiple purposes, one of which is tocreate electricity to be sold into the local electric utility grid. Itcan also be used locally for private or micro grid electric powerapplications, or combinations thereof. Natural gas generators can beutilized with a variety of natural gas applications such as oilfieldflare gas and landfill methane, thereby utilizing and reducing wastegases that would otherwise contribute to global greenhouse gasaccumulation. The process creates a highly useful, efficient,commercially viable environment for the disposal of waste flare gas(greenhouse gas), processes oilfield salt water waste (highly toxic andenvironmentally damaging when pumped underground to saltwater disposalwells which creates local earthquakes and groundwater contamination),captures waste CO₂ in a highly efficient form (greenhouse gas), andreleases potable water for downstream consumption in various forms.

The extreme heat released by the natural gas generator exhaust flue isused to heat and process the water into high quality steam, separatingthe majority of salt and contaminants from the water, leaving potablewater that can be permitted and released to the environment or sold foragricultural or industrial use such as oilfield activities. Thissaltwater processing for oilfield solutions provides a solid revenuestream with greatly reduced environmental impacts such as earthquakes,downhole pumping, chemical dumping, or groundwater contamination. Theprocessed water will be directed into a permitted cooling pond orapparatus, not injected into underground strata. The processed waterwill instead be permitted to be placed into a local stream or localirrigation as potable water and sold as a third revenue stream. Anadditional system will recover high pressure CO₂ derived from the systemusing high pressure steam generated by the unit. This high pressure CO₂is salvaged, converted to liquid, and sold or used for industrial oragricultural processes as a fourth revenue stream, reducing CO₂ outputto the atmosphere and reducing output of greenhouse gases.

The present invention thus recovers the energy wasted through electricalenergy generation, heat, and exhaust, and maximizes efficiency of theenergy processes associated with generation, desalination and CO₂recovery by capturing these processes as they occur. The presentinvention thus provides for an ultra-high efficiency impact from theelectricity generation unit with the coupling of these systems fromstandard industrial practices.

Thus, it should be understood that the embodiments and examplesdescribed herein have been chosen and described in order to bestillustrate the principles of the invention and its practicalapplications to thereby enable one of ordinary skill in the art to bestutilize the invention in various embodiments and with variousmodifications as are suited for particular uses contemplated. Eventhough specific embodiments of this invention have been described, theyare not to be taken as exhaustive. There are several variations thatwill be apparent to those skilled in the art.

1-5. (canceled)
 6. A desalination system, comprising: an electricitygenerator adapted to generate electricity from combustion, furthergenerating exhaust heat; a heat exchanger adapted to receive the exhaustheat from the electricity generator and directly receive a saltwater orbrackish water stream and to apply the heat from the generator exhaustto said stream comprising water and salt, wherein the heat exchangerconverts the water to steam so as to separate the water from a majorityof the salt; and a condenser adapted to condense the steam to distilledwater.
 7. The desalination system of claim 6, wherein the electricitygenerator further exhausts carbon dioxide from the combustion, thesystem further comprising a carbon dioxide scrubber adapted to removecarbon dioxide from the exhaust stream.
 8. The desalination system ofclaim 7, further comprising apparatus configured to liquify and storethe removed carbon dioxide.
 9. The system of claim 6, further comprisinga storage area in fluid communication with the heat exchanger, whereinthe storage area stores the saltwater or brackish water, and the storagearea is in fluid communication with the heat exchanger.
 10. Thedesalination system of claim 6, wherein the water stream containscontaminants in addition to the water and salt, and the heat exchangerfurther separates the water from a majority of the contaminants.
 11. Anoil field comprising the desalination system of claim
 6. 12. A methodfor conserving energy in a desalination unit, comprising the steps of:operating an electrical generator to generate electricity and an exhauststream comprising heat; directing saltwater or brackish water into aheat exchanger; directing the exhaust stream into said heat exchanger;applying heat from the exhaust stream within the heat exchanger toconvert water in the saltwater or brackish water within the heatexchanger to steam, thereby separating water of the saltwater orbrackish water from at least a majority of salt of the saltwater ofbrackish water; removing the steam to leave behind the majority of saidsalt; and condensing the steam to produce potable water.
 13. The methodof claim 12, further comprising the steps of: removing carbon dioxidefrom the exhaust stream.
 14. The method of claim 13, further comprisingthe step of liquefying the carbon dioxide.
 15. The method of claim 14,further comprising the step of receiving revenue from sale of the carbondioxide.
 16. The method of claim 12, further comprising the step ofreceiving revenue for treatment of the saltwater or brackish water. 17.The method of claim 12, further comprising the step of receiving revenuefrom sale of the generated electricity.
 18. The method of claim 17,further comprising the step of generating electricity through atransformer prior to the step of receiving revenue from sale of thegenerated electricity.
 19. The method of claim 12, further comprisingthe step of receiving revenue from sale of the potable water.
 20. Themethod of claim 12, wherein the saltwater or brackish water furthercomprises contaminants, and the removing step further leaves behind amajority of said contaminants.
 21. The method of claim 12, furthercomprising the step of storing the saltwater or brackish water in astorage tank, and directing the saltwater or brackish water from thestorage tank to the heat exchanger.
 22. The method of claim 12, whereinthe operating step comprises operating the generator on natural gas.